[FFmpeg-user] ProRes422 with 8 audio tracks converted to mp4 -- muffles audio 4

[Carl Eugen Hoyos]

2018-11-20 12:05 GMT+01:00, Carl Eugen Hoyos <ceffmpeg at gmail.com>:
> 2018-11-20 4:28 GMT+01:00, Harvey Pikelberger <communque at gmail.com>:
>> Testing the creation of 8-audio-channel mp4 proxies from ProRes422
>> sources using ffmpeg. For some reason audio channel 4 of the mp4
>> is coming back muffled, like it got drowned in a pool.
>
> Every aac encoder will assume that one of eight input channels is the
> lfe channel and will only encode low frequencies for this channel.
> (Maybe not "every" but in any case, this is the issue you see.)

In case I misunderstood the issue and this is really 7.1 input but the
encoding is broken: Our aac encoder provides acceptable output for
mono and stereo, maybe not for other layouts and there is an
unavoidable issue for 7.1 aac because of a flaw in the specification,
feel free to test with the libfdk aac encoder.

Carl Eugen